Inertia switch

ABSTRACT

An inertia switch having a two-part housing of electrical insulating material, the lower housing part being provided with a conical ramp surface at its bottom to receive a relatively heavy ball which is adapted to move along the ramp surface in the event of a collision by an automobile, for example, to tilt a disc of electrical conductive material into contact with a flat electrical conductive ring. The ring is provided with a lead in the form of a tab extending through a notch in the housing part to the outside to receive suitable wires or leads. In engagement with the disc and extending through the center of the ring is a coil spring also of electrical conductive material, the upper end of which is disposed in a guide which is rigid with the inside of the upper housing part. Fixed within the guide and engaged by the coil spring is a conductive strip which extends to the outside of the housing through a notch in the housing part for the reception of a wire. The upper housing part has a depending flange which fits frictionally into the lower housing part to hold the housing parts together and also to bear against the conical ramp may be built-up by increasing the wall thickness to serve as a block for reducing the effective scope of the switch.

United States Patent [72] Inventor Arthur A. Hitchcock Cridersvllle, Ohio [2]] Appl. No. 3,671 [22] Filed Jan. 19, 1970 [45] Patented Nov. 16, 1971 [73] Assignee A.C.B. Corporation Lima, Ohio [54] INERTIA SWITCH 4 Claims, 3 Drawing Figs.

[52] U.S. Cl 200/6L45 [51] Int.Cl H0lh 35/14 [50] Field of Search 200/61 .45-61 .53, 262, 52; 340/261 [56] References Cited UNITED STATES PATENTS 1,414,932 5/1922 Chisman ZOO/61.45 2,415,086 2/1947 Detwiler ZOO/61.45 3,158,705 11/1964 Bliss ZOO/61.45 3,198,899 8/1965 Hitchcock ZOO/61.45

Primary Examiner Robert K. Schaefer Assistant Examiner-M. Ginsburg Attorney-Malcolm W. Fraser ABSTRACT: An inertia switch having a two-part housing of electrical insulating material, the lower housing part being provided with a conical ramp surface 'at its bottom to receive a relatively heavy ball which is adapted to move along the ramp surface in the event of a collision by an automobile, for example, to tilt a disc of electrical conductive material into contact with a flat electrical conductive ring. The ring is provided with a lead in the form of a tab extending through a notch in the housing part to the outside to receive suitable wires or leads. ln engagement with the disc and extending through the center of the ring is a coil spring also of electrical conductive material, the upper end of which is disposed in a guide which is rigid with the inside of the upper housing part. Fixed within the guide and engaged by the coil spring is a conductive strip which extends to the outside of the housing through a notch in the housing part for the reception of a wire.

The upper housing part has a depending flange which fits frictionally into the lower housing part to hold the housing parts together and also to bear against the conical ramp may be built-up by increasing the wall thickness to serve as a block for reducing the effective scope oi'the switch.

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A Tvomuev switch is required.

1 means swrrcn A desideratum exists for a simple, efficient, and foolproof inertia switch particularly for automobiles, which is capable of functioning only in major accidents, and not as a result of minor maneuvers. Such switch must be effective in the event of a major collision, for example, to trigger safety devices. such as an air bag, fire extinguisher, or deenergizing devices. Much effort and expense have been expended in this connection but the results have not been satisfactory. The switches have been too complex, too expensive, or so delicate they will not stand up under normal usage.

Reference is hereby made v Aug. 3, I965, which shows a circuit breaker for vehicles including an inertia operated switch. Although the mechanism therein shown and described is highly satisfactory for certain uses, it is too complex and expensive where a simpleinertia SUMMARY or THE INVENTION A simple switch mechanism is produced which has the unique ability automatically to determine when the desired combination of G forces and time have been attained, such, for example as may develop in an automobile collision. It can maintain an electric circuitfor a time durationduring an automobile crash, and reset itself instantly when the G force exerted is reduced to a minimum. The ability to reset itself immediately results that an electric circuit will be maintained only for the duration of the existing G forces. Transitory G forces, no matter how great, if they are not maintained longer than the required time for the electrical surge, cannot operate the switch.

The structure involved consists of a two-part, housing which has bracket means enabling it to be mounted in a useful position and the housing parts are held together by frictional engagement. In the lower housing part is a conical ramp on which a relatively heavy ball, such as a steel ball, can freely roll. The lower housing part has two vertically spaced ledges of different diameters, the lower ledge having the shorter diameter and receiving a flat electrical conductive disc. The upper ledge receives a flat electrical conductive ring, which has a lead in the form of a tab extending through a notch in the casing to the outside to receive a suitable wire. In the upper housing part is a guided coil spring of electrical conductive material, which is in constant engagement with the upper face of the flat disc at one end. The opposite end of the coil spring engages a conductive strip which extends through a notch in the upper housing part to the outside to receive the suitable lead.

For restricting the action of the ball and reducing the scope of the switch, a portion of the chamber directly above the conical ramp may be enlarged to block movement of the ball in that direction.

BRIEF DESCRIPTION OF THE DRAWINGS DESCRIPTION OF THE PREFERRED EMBODIMENTS The illustrated embodiment of the invention shown in FIGS. 1 and 2 comprises a vertically disposed housing which is of an electrical insulating or nonconducting material, such as molded plastic material. The housing consists of two parts, an upper part and a lower part 11. On the lower part II is a to U.S. Pat. No. 3,198,899 issued are apertured to receive 2 pair of oppositely extending integral 'bracketarms I2, which screws for connecting the switch assembly to a suitable support. In the lower housing pan 1!, which is in the shape of an inverted dome, there is a chamber having a cylindrical sidewall 13 and a conical ramp'surface l4 upon the ramp surface 14 is a ball 15 constituting a spherical mass of high-density material, such as l8 rests loosely on the ledge 16 so that it can be canted or tilted readily into engagement with a flatring I9 also of electrical conductive material, which rests 'on the upperledge 17. The flat ring 19 has a lead-in the form of a lateral tab provided with a reduced neck to fit a notch 21 in the upper portion of the housing part 11. The tab extends outsideof the housing to receive asuitable wire. W s v g A Engaging a central portion of the flat disc l s is a coil spring 23 of electrical conductive material. Manifestly, the spring passes freely through the opening inthe ring 19 and the upper end fits over a short metallic tube 24 which may be electrically conductive and which is rigid with an electrical conductive as shown 'in FIG. 2, I the flange abutting against the rim portion of the hold it properly in position.

The coil spring 23 is retained in position by a tubular guide 27 which is fixed at its upper end to the inner wallof the upper housing part 10. The housing partl0 is d o'me shaped. The

circular disc 18 away from its ledge and into contact with the flat ring 19, thereby to close the switch. Wlien theG force has been reduced to the preset minirn um, the balllSmovesdown the ramp assisted by the weight of the disc 18 and the pressure exerted by the coil spring 23. As soon back down the ramp 14, contact is brokenibetween the disc 18 and the ring 19, thereby opening the switch. It 'willbe manifest that opening of the switch is not retarded by friction so that there is no chance of the switch sticking in closed position. As above mentioned, the diameter of the disc I8 is considerably less than the outer'diameter of the ledge I6 on whichit rats, and this militates against sticking or jamming of the disc I8 in the housing. This also affords a wiping action by the disc [8 against the flat ring 19 as the SWItCh IS closed and opened, which assures clean contacts with good conductivity. I

It should be understood that the switch will not operate even though a severe impact takes place so long as the forward motion of the vehicle does not continue at least to a small degree. It is important that there be at least some slight motion whether it be forward, rearward,

sistance slightly greater than that experienced in a sev ere rak ng maneuver and existing for a split second of time. the electrical contacts will then be established.

In some instances, the switch may not be required to work through an arc of 360 as shown in FIGS. 1 and 2, and. as shown in FIG. 3, the wall of the chamber above the ramp is ,enlarged on that side which is to be blocked. A filler piece 29 is applied to the chamber directly above the conical ramp surface thereby preventing actlon of the ball on the portion hav- 1. An inertia switch comprising a two-part upright housing of electrical insulating material, the lower part having an open-mouthed chamber having as its bottom wall a conical ramp surface, a relatively heavy ball in said chamber for movement along said ramp surface, a pair of vertically spaced ledges adjacent the open mouth of said chamber with the lower ledge of less diameter than the upper ledge, a flat disc of electrical conductive material seated loosely upon said lower ledge, a flat ring of electrical conductive material on said upper ledge, a tab rigid with said ring and extending laterally from the rim thereof, a notch in said lower housing part adjacent said upper ledge to receive said tab and enable the latter to extend outside of said housing, a depending flange on said upper housing part to fit the lower housing part and bear against said ring for holding same in place, a coil spring guide depending from said upper housing part, a coil spring of electrical conductive material associated with said spring guide extending through said ring and bearing against said disk at its lower end, a conductive strip engaged at one end portion by said coil spring and extending laterally therefrom outside of the housing, and a notch in said upper housing part through which said strip extends.

2. An inertia switch as claimed in claim 1, comprising lateral brackets on one of said housing parts enabling mounting thereof.

3. An inertia switch as claimed in claim 1, in which said coil spring guide comprises a cylindrical member rigid with the inner wall of said upper housing part provided with a lateral aperture through which said strip extends.

4. An inertia switch as claimed in claim 1, comprising blocking means in said chamber for preventing effective movement of the ball throughout the blocked area, said blocking means increasing the thickness of the walls of a part of the chamber. 

1. An inertia switch comprising a two-part upright housing of electrical insulating material, the lower part having an openmouthed chamber having as its bottom wall a conical ramp surface, a relatively heavy ball in said chamber for movement along said ramp surface, a pair of vertically spaced ledges adjacent the open mouth of said chamber with the lower ledge of less diameter than the upper ledge, a flat disc of electrical conductive material seated loosely upon said lower ledge, a flat ring of electrical conductive material on said upper ledge, a tab rigid with said ring and extending laterally from the rim thereof, a notch in said lower housing part adjacent said upper ledge to receive said tab and enable the latter to extend outside of said housing, a depending flange on said upper housing part to fit the lower housing part and bear against said ring for holding same in place, a coil spring guide depending from said upper housing part, a coil spring of electrical conductive material associated with said spring guide extending through said ring and bearing against said disk at its lower end, a conductive strip engaged at one end portion by said coil spring and extending laterally therefrom outside of the housing, and a notch in said upper housing part through which said strip extends.
 2. An inertia switch as claimed in claim 1, comprising lateral brackets on one of said housing parts enabling mounting thereof.
 3. An inertia switch as claimed in claim 1, in which said coil spring guide comprises a cylindrical member rigid with the inner wall of said upper housing part provided with a lateral aperture through which said strip extends.
 4. An inertia switch as claimed in claim 1, comprising blocking means in said chamber for preventing effective movement of the ball throughout the blocked area, said blocking means increasing the thickness of the walls of a part of the chamber. 